Circuit Description Of Tel/Liu Pwb; Block Description - Sharp UX-108 Service Manual

[3] Circuit description of TEL/LIU PWB

(1) TEL/LIU block operational description
1) Block diagram
TEL
HS DETECTOR
LINE
EXT.
HANDSET
H
SPEAKER
L
L H
2) Circuit description
The TEL/LIU PWB is composed of the following 7 blocks.
1. Speech circuit section
2. Dial transmission section
3. Speaker amplifier section
4. Ringer circuit section
5. Externally connected TEL OFF HOOK detection circuit
6. CI detection circuit
7. Signal/DTMF transmission level & receiving level
TEL/LIU PWB
CML
TX OUT
H
L
CI DETECTOR
RC VOL2
TEL IN
TEL OUT
VOL A
SP AMP
SP OUT
CONTROL PWB
CML
TX CONT
1
0
RX IN
0
1
RC VOL1
VOL B
0
1
Fig. 5

3) Block description

1. Speech circuit section
•
The receiver volume is an electronic volume type, this model is
switch in 3 steps.
2. Dial transmission section
•
D.P. transmission: The CML relay is turned on and off for control in
the DP calling system. (Refer to the attached sheet.)
•
DTM transmission: It is formed in the modem, and is output.
3. Speaker amplifier section
•
The volume of the ringer sound/speaker sound is controlled with
2-bit signal of VOLA and VOLB, and the sound switch is controlled
with BZ CONT.
4. Ringer circuit section
•
The ringer sound is formed in the tone of 1-chip engine when CI
signal is detected. The amplifier circuit drives the speaker of the
main body.
5 – 8
GAIN-C
SIGTX
MODEM
(R96DFXL-CID)
SIGRX
BZOUT
XFC3
BZ CONT
SP MUTE
TEL MUTE
CI
HS
UX-108U/178U/188U
FO-375U
RC VOL2
RC VOL1
GAIN-C
TXCONT
CML